The research described in this proposal is part of a larger research program designed to investigate basic, elemental cognitive processes in humans. Here we focus on the classic problem of stimulus-response compatibility. A new model is proposed that is broadly based on basic principles of human information processing. We will examine the role of automatic and controlled processing mechanisms underlying stimulus-response compatibility. Our objective is to provide a systematic account of performance in highly compatible, incompatible and non-compatible tasks; simultaneously to acquire a better understanding of the fundamental cognitive processes that govern performance in such tasks; relate this work to the central problems in cognition, and extend it to cognitive search on schizophrenia, and psychopathology in general. Twelve experiments are proposed and divided into four series. The first series of experiments is designed to test the model's predictions in two basic experimental paradigms and aims at distinguishing between the weak and the strong forms of the model. The second series is designed to obtain precise information on the time course of the automatic activation process postulated by the model. The third series deals with the processing consequences of correlated and uncorrelated overlapping dimensions. And the fourth series evaluates the feasibility of using stimulus-response compatibility tasks in research on schizophrenia and other psychopathologies. The empirical and theoretical results that we expect to obtain promise to advance our understanding of human cognitional do performance in normals as well as in patients suffering from schizophrenia and other cognitive dysfunctions.